Abstract
Cyanine dyes of zero/bis-zero methine incorporating imid-azo(1,2-a)Pyridine (quinoline) or pyrazino(1,2-a)pyridine (quinoline) with stable C-N bond were synthesized using keto-oxime methylene C-link heterocyclic quaternary salts [1-phenyl-3-methyl-pyrazolino-4-keto-oxime-α-methylene-bis-pyridin-(quinoin)-1(4)-di-ium-iodide(ethiodide) salts and 1-phenyl-3-methyl-pyrazolino- 4-ketooxime-α-methylene-N-2-methyl-bis pyridin (quinoin)-1(4)-di-ium-iodide(ethiodide) salts]. Such heterocyclic precursors and related dyes were identified by elemental and spectral analyses. The absorption spectra properties of such dyes were investigated in 95% Ethanol to attempt and throw some light on the influence of such new heterocyclic nuclei and to compare or evaluate spectral behaviors. The absorption spectra of dyes in different pure solvents were examined in the visible region showing solvatochromism and the colour changes of dyes with solvents having different polarities. This permits a selection of the optimal solvent (fractional solvent) when such dyes are applied as photosensitizers. The spectral behavior of some selected newly synthesized cyanine dyes is observed in mixed solvents of different polarities and progressively increasing quantities of one solvent over the other were studied and showed an increase in the absorbance of CT band with increasing proportion of that solvent. Evidence for hydrogen bond formation between the solute molecules and solvent molecules allows measurement of certain energies such as hydrogen bonding, orientation, and free energies.
Highlights
Special attention is given to the implementation, preparations, and applications of heterocyclic cyanine dyes to show the various aspects in order to satisfy the great demand in industrial, physiology, biochemistry and various biological fields
N-bridge head heterocyclic compounds used as precursors possess high site reactivity susceptible to be attacked by either Electrophile/Nucleophile in the substitution/addition reactions which give high stability nature for the dyes [17]
Dye Synthesis The synthesis of zero methine (4a, b & 5a, b) and bis-zero methine (6a-f) cyanine dyes was started by preparation of 3-methyl-1-phenyl-pyrazolin-4,4-ketomethylene-quinolin-1-ium ethiodide salts (1) according to reference [26] followed by the reaction of an ethanolic solution of (1) with hydroxyl amine in the presence of sodium acetate to afford 3-methyl-1-phenyl-pyrazolin-4,4-ketooximemethylene-pyridine-1-ium ethiodide salt (2)
Summary
Special attention is given to the implementation, preparations, and applications of heterocyclic cyanine dyes to show the various aspects in order to satisfy the great demand in industrial, physiology, biochemistry and various biological fields. Cyanine dyes are colorant compounds used in staining of internal limiting membrane (ILM) [1] [2] [3], as fluorescent dyes in DNA detection [4] [5] [6] [7], optical sensors [8] [9], organic photoconductors [10], vulcanizing accelerator agents, photographic sensitizers [11], solar cell [12] This multi-property and numerous applications of cyanine dyes push the scientist to design and improve synthetic procedure of new cyanine dyes based on N-bridgehead heterocycles [13] [14], which are characterized by outstanding chemical stability, absorb at long wavelength [15] [16], high solubility and change their optical, thermal or electronic properties to meet the requirements for opto-electronic or biological products. The spectral, solvatochromic behavior and mixed solvent effect are described
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